Method, system and apparatus for detecting injector closing time

ABSTRACT

A method for detecting a closing time of an injector valve includes receiving a valve current profile of the injector valve, processing the valve current profile using at least a slope discriminator, determining a stuck status and a closing time (if applicable) of the injector valve based on an output of the slope discriminator. An engine control unit configured to detect a closing time of an injector valve is also provided. The engine control unit has a first control logic configured to receive a valve current profile of the injector valve, a second control logic configured to process the current profile using at least a slope discriminator, and a third control logic configured to determine a stuck status and a closing time of the injector valve based on an output of the slope discriminator. Further, a vehicle system including a controller configured to detecting a valve closing time is provided.

TECHNICAL FIELD

The present disclosure relates generally to injector controls, and morespecifically to a process, system, and apparatus for detecting a closingtime and status of a solenoid injector.

BACKGROUND OF THE INVENTION

The global drive to reduce NOx and CO2 emissions from diesel engineexhausts has led to the implementation of selective catalytic reductionsystems in diesel engine vehicles to reduce the automotive emissions.Selective catalytic reduction systems operate by adding a gaseous orliquid reductant to the exhaust gas stream from an engine. The gaseousor liquid reductant is absorbed onto a catalyst where the reductantreacts with nitrogen oxides in the exhaust gas to form water vapor andnitrogen.

This treatment requires the reducing agent to be administered at aprecise concentration and with high quality. The solution must beaccurately metered and injected into the exhaust gas stream, where it ishydrolyzed before converting the nitrogen oxide (NOx) to nitrogen (N2)and water (H2O).

As the tailpipe NOx emission standard becomes increasingly stringent, itis desired to diagnose the injection faults to assist with the SCR DeNOxfunctionality and performance. For example, a stuck injector may causeunder-dosing of urea and thus reduced DeNOx functionality.

In order to properly interact with on-board diagnostic systems, such asOBD or OBDII, existing selective catalytic reduction systems includeself-diagnostics to identify faults and enable pin point replacementwhile the vehicle is being serviced. For example, pressure changes maybe monitored after commanding the pump to run or shut down. One drawbackof this method, however, is that the emissions control process isdisrupted. Accordingly, new systems and methods of detecting the SCRclosing time are desired.

In addition, determining closing time of injectors for direct fuelinjection is also desired, in order to provide for better control andimproved fuel economy.

SUMMARY OF THE INVENTION

Disclosed is an apparatus, system, and method for detecting a closingtime of a valve, such as an SCR valve or a direct injection valve,without additional hardware and without disrupting the emissions controlprocess. The invention may include employing a digital filter and aslope discriminator is developed, which enables a diagnostic function toaccurately detect injector closing time and reliably identify a stuckclosing injector by monitoring injector current on aninjection-to-injection basis.

In one form, a method for detecting a closing time of an injector valveis provided. The method includes receiving a valve current profile ofthe injector valve, processing the valve current profile using at leasta slope discriminator, determining a stuck status of the injector valvebased on an output of the slope discriminator, and if the injector valveis not stuck, determining the closing time of the injector valve basedon the output of the slope discriminator.

In another form, an engine control unit configured to detect a closingtime of an injector valve is provided. The engine control unit includesa first control logic configured to receive a valve current profile ofthe injector valve, a second control logic configured to process thevalve current profile using at least a slope discriminator, and a thirdcontrol logic configured to determine a stuck status and a closing timeof the injector valve based on an output of the slope discriminator.

In yet another form, a vehicle system is provided that includes anexhaust system including an injector and at least one sensor operable todetect a current draw of the injector. The vehicle system also includesa controller connected to the at least one sensor. The controller isoperable to receive a profile of the current draw of the selectivecatalytic reduction injector and to process the profile using a slopediscriminator. The controller is also operable to determine a stuckstatus and a closing time of the injector based on an output of theslope discriminator.

In still another form, the present disclosure provides a non-transitorymachine-readable medium that provides instructions, which when executedby a machine, cause the machine to perform operations. The operationsinclude receiving a valve current profile of the injector valve,processing the valve current profile using at least a slopediscriminator, and determining a stuck status and a closing time of theinjector valve based on an output of the slope discriminator.

In still another form, a method for controlling an injector is provided.The includes the steps of: instructing an injector to begin closingusing a controller; receiving an injector current profile of theinjector at the controller; processing the current profile using atleast a slope discriminator in the controller; and determining stuckstatus and a closing of the injector based on an output of the slopediscriminator.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are provided for illustration purposes only, andare not intended to limit the scope of the present application andclaims:

FIG. 1 is a schematic side view of a vehicle including a selectivecatalytic reduction injector for reducing emissions, in accordance withthe principles of the present disclosure;

FIG. 2A is a graph of a current profile of a selective catalyticreduction injector and a current profile of a stuck selective catalyticreduction injector with respect to time, according to the principles ofthe present disclosure;

FIG. 2B is a zoomed-in portion of the graph of FIG. 2A, illustrating acurrent profile of a selective catalytic reduction injector and a stuckselective catalytic reduction injector at and around closing time, inaccordance with the principles of the present disclosure;

FIG. 3 is a block diagram illustrating a process for detecting a closingtime and status of an injector, according to the principles of thepresent disclosure;

FIG. 4 is a graph illustrating a slope discriminator scheme for theprocess of FIG. 3, in accordance with the principles of the presentdisclosure; and

FIG. 5 is a graph illustrating an output chart of a slope discriminator,according to the principles of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a vehicle 10 including an exhaustsystem 20 for expelling exhaust 30 from an internal combustion engine ofthe vehicle 10. The exhaust system 20 includes a selective catalyticreduction injector 40 that adds a gaseous or liquid reductant to theexhaust gas stream from the engine. The gaseous or liquid reductant isabsorbed onto a catalyst where the reductant reacts with nitrogen oxidesin the exhaust gas to form water vapor and nitrogen. The selectivecatalytic reduction injector 40 is controlled by a controller 50, andincludes a sensor package capable of sensing inputs to and outputs fromthe selective catalytic reduction injector 40. In one example, theinjector 40 is in the form of a solenoid valve.

One of the inputs that the sensor package can detect, and communicateback to the controller 50, is a current draw of the selective catalyticinjector 40. This current draw can be aggregated by the controller 50 todetermine a current profile of the selective catalytic reductioninjector 40. Based on the current profile of the selective catalyticreduction injector 40, the controller 50 can determine a preciseinjector closing time and whether the injector is stuck or unstuck usingthe below described process.

The current profile of the selective catalytic reduction injector 40 isa function of battery voltage supplied to the injector, injectortemperature and injector fluid pressure. At the conditions of lowtemperature, low pressure, and high voltage, the current profile of anominal selective catalytic reduction injector 40 is almost the same as(superficially similar to) a stuck selective catalytic reductioninjector, and a top level, or visual, inspection of the current profileis insufficient to identify a stuck injector or to precisely identifythe closing time of the injector 40.

Though an SCR injector 40 is shown in FIG. 1, it should be understoodthat any type of solenoid injector could be used, such as a solenoidport fuel injector or a solenoid direct fuel injector. Solenoid fuelinjectors also have a current draw, from which a current profile can beaggregated by a controller, such as controller 50. Accordingly, theprinciples described here may apply to a solenoid fuel injector, as wellas an SCR injector 40, or any injector with an inductance reaction uponopening or closing.

With continued reference to FIG. 1, FIGS. 2A-2B illustrate a currentprofile 110 of a selective catalytic reduction injector 40 and a currentprofile 120 of a stuck selective catalytic reduction injector 40 withrespect to time. FIG. 2B is an enlarged view of the end of injection.When the injector 40 is desired to be closed, the current is clamped andthe injector begins to close at a time period c. After a delay period d,the non-stuck injector 40 has a post-clamp hump 112 in its currentprofile 110, and the stuck injector 40 has a post-clamp hump 114 in itscurrent profile 120. The post-clamp hump 112 of the non-stuck injectoris larger than the post-clamp hump 114 of the stuck injector, that is,the injector that does not fully close. The delay period d is acalibration value. The purpose of delay is to reduce the length ofinjector current data buffer, and avoid injector current clamp.

A data collection window of a current profile 110, 120 is the windowduring which the analog-to-digital converter (ADC) of controller 50collects injector current profile data for detecting the current drawnby the injector 40. The ADC of controller 50 can be configured to readand filter injector closing data with a high sampling rate. During thiswindow 116, the injector closing current data is processed by the ADC ofcontroller 50 and stored in a data buffer. The data in the buffer can befed to a slope discriminator to determine the selective catalyticreduction injector 40 stuck status and closing time. The slopediscriminator can be another controller, a software module stored in amemory of the controller 50, or any other similar system. For example,the controller 50 can be configured to receive the valve current profile110, 120, process the valve current profile with the slopediscriminator, and determine the stuck status and the closing time (ifapplicable) of the injector valve based on the output of the slopediscriminator.

With continued reference to FIG. 1, FIG. 3 illustrates a process 200utilized by the controller 50 to detect the stuck status and closingtime of the selective catalytic reduction injector 40. As describedabove, the process 200 may alternatively apply to a solenoid fuelinjector, rather than an SCR injector 40. Initially, the controller 50checks to see if injection has ended in an end of injection check step210. If injection has not ended, the process 200 loops back, and the endof injection check step 210 is performed again after any suitable delay.

If injection has ended, the process 200 starts a delay timer in step212. The delay timer step 212 causes delay for a predetermined,calibrated period of time. As illustrated in FIG. 2B, there is a delayperiod d between when the injection ends and when the detection window116 opens. In the step 212, the controller 50 waits the delay periodbetween the end of injection and the beginning of the detection window116 before moving on to detect the stuck status and closing time.

Next, the process 200 moves to a check step 214 of whether the delaytimer has expired. If the delay timer has not expired when thecontroller 50 performs the delay timer expired check 214, the process200 loops back to wait for the delay timer to expire and checks again atstep 214. The delay timer is updated every time when the function isexecuted.

If, however, the delay timer has expired, the controller 50 beginscollecting and filtering current data to construct an injector closingcurrent profile of the injector 40 in a collect injector closing datastep 218. The current data can be processed using any acceptable sensorarrangement. In some examples, the current data is collected using anextremely high sampling rate. The sampling rate is the rate at whichdata samples are detected. By way of example, a sampling rate of 1microsecond corresponds to one current detection occurring everymicrosecond, and this sampling rate may be used in the currentapplication.

After the collect injector closing data step 218, the process moves to acheck step 220 to determine whether data collection is complete. If datacollection is not complete, the process 200 loops back around to thecollect injector closing data step 218, in the collection window 116.After it is determined in step 220 that data collection is complete, theprocess 200 moves to step 222.

In order to reduce the detected current data to a manageable conditionand amount, the detected data may be filtered by the controller 50 toremove high frequency noise using a standard digital filter. In exampleutilizing a high sampling rate, the data may be further downsampledusing known downsampling techniques to reduce the amount of data in thecurrent profile. The filtered and downsampled data forms an injectorclosing current profile, such as the current profiles 110, 120illustrated in FIGS. 2A-2B. The processed injector closing currentprofile data is stored in the injector closing data buffer. Once thecurrent profile has been determined, the controller 50, or anotherdevice, applies a slope discriminator process to the current profile inan apply slope discriminator step 222. Because the injector closingcurrent profile data has been stored in the buffer, the steps 222, 224and 226 can be executed according to systems task scheduling. Theprocess performed by the slope discriminator is described below ingreater detail with regards to FIG. 4.

The slope discriminator may utilize nonlinear digital filteringtechniques to distinguish the difference in the slope between a stuckinjector and a non-stuck injector during closing time. Thus, after thestep 222 of applying the slope discriminator, the process 200 moves onto determine the injector closing time (if not stuck) and/or the stuckstatus of being stuck or not stuck in step 224.

Once the closing time and/or stuck status of the injector 40 has beendetermined, the controller 50 reports the stuck status and/or theclosing time in a report closing time and status step 226. The reportingcan be to another separate controller, a subprogram within thecontroller 50, or a diagnostic system, such as an OBD (On-BoardDiagnostic) or OBDII (On-Board Diagnostic II). Alternately, the closingtime and status can be reported to any other system where the openingtime and status of the injector 40 is needed.

With continued reference to FIG. 1, FIG. 4 is a graph 300 illustrating acurrent profile 302 of an injector 40, which shows the principles of theslope discriminator. As described above, in order to determine thecurrent profile 302, the controller 50 may utilize a nonlinear digitalfiltering technique to remove noise and downsamples the data to decreasethe amount of data, thereby decreasing the data buffer size. Once thecurrent profile 302 has been determined, the controller 50 applies theslope discriminator.

The slope discriminator utilizes a modified median filter to determine aslope of the injector profile 302. The slope discriminator processes thecurrent profile 302 entry by entry, replacing each entry with thecentered value of neighboring entries falling within a median window 320to determine a median current profile. The entries within the medianwindow 320 are then sorted in increasing value. The slope discriminatorfurther processes the current profile 302 entry by entry, replacing eachentry with the mean value of neighboring entries falling with a meanwindow 310 to determine a mean current profile.

As can be seen in FIG. 4, the mean window 310 is a smaller window(encompasses fewer neighboring data points) than the median window 320.Further, the mean window 310 falls entirely within the median window320. The starting edge of the mean window 310 may be offset from thestarting edge of the median window 320 by an offset value. The size ofboth the mean window 310 and the median window 320, as well as the sizeof the offset, are calibration values that can be experimentally ormathematically determined for a particular selective catalytic reductioninjector 40 by one of skill in the art having the benefit of thisdisclosure. Due to the required size of the windows 310, 320, theinitial output of the slope reflection detection process occurs at point340, and not at a start time 304 of the current profile 302. In theillustrated example of FIG. 4 the initial output 340 of the slopediscriminator occurs at the end point of the initial mean window 310.

The value of the output at point 340, and all output values 302, isdetermined by the following relationship:Output=median term*gain factor for median term−(mean term*gain factorfor mean term−offset term);

where Output is the output value;

median term is the center value of the median window 320, which iscalculated in sliding window 320 entry by entry;

mean term is the mean value of the mean window 310, which is calculatedin sliding window 310 entry by entry;gain factor for median term=1+abs(median term−mean term); andgain factor for mean term=1−abs(median term−mean term);offset term=abs(median term−mean term)/length of median sliding window320.

As known in mathematics, “abs” is the absolute value function. Thus, thegain factors are variable gain factors, which depend on the differencebetween the median term and the mean term. The gain factor for themedian term is always greater than or equal to one; and the gain factorfor the mean term is always less than or equal to one. The offset termis also related to the difference between the mean term and the medianterm.

As a result of the above relationships, the bigger the differencebetween the value of the median window 320 and the mean window 310, thegreater the factor gain factor for the median term will be. Similarly,the bigger the difference between the value of the median window 320 andthe mean window 310, the smaller factor gain factor for the mean termwill be. This difference in the gain factors results in an output termthat greatly magnifies the slope, thus showing a separation between thestuck injector current profile and the non-stuck injector closingprofile at closing time.

With continued reference to FIGS. 1 and 4, FIG. 5 illustrates an outputgraph 400 showing outputs of the slope discriminator for non-stuck andstuck SCR injectors 40. The outputs for a normal, non-stuck injector aregraphed at line 410, and the outputs for a stuck injector are graphed atline 420. The location of the maximum value 422 of the normal injectoroutput plot 410 indicates that the SCR injection needle is fully closed.Since there is a large separation between the stuck and non-stuckprofiles 420, 410, a predetermined calibrated threshold 424 can bedetermined, to which the profiles 410, 420 can be compared. For example,if any of the profile 410, 420 is above the threshold 424, then the SCRinjector can be determined to be non-stuck; and if any of the profile410, 420 is below the threshold 424, the SCR injector can be determinedto be closed. Based on this difference, the controller 50 can detectwhen the selective catalytic reduction injector 40 is stuck (i.e. whenany of the output profile 410, 420 exceeds the predetermined threshold424).

The precise injector closing time can be easily calculated based on thelocation of the maximum value 422. The precise closing time of theselective catalytic reduction injector 40 is precise to within a timeperiod of the downsampled data rate. Thus, if the downsampled data rateis 1 microsecond, the time of the maximum value point 422 can fallwithin 1 microsecond of the actual fully open time of the selectivecatalytic reduction injector 40, depending on the system tolerances andslope discriminator filter calibration.

By utilizing the above described process, the controller 50 candetermine the precise closing time of a selective catalytic reductioninjector and whether the selective catalytic reduction injector is stuckor non-stuck. As can be appreciated by one of skill in the art havingthe benefit of this disclosure, the above described process can beapplied to any number of injector valves exhibiting similar slopereflection characteristics, and is not limited to selective catalyticreduction injectors.

It is further understood that any of the above described concepts can beused alone or in combination with any or all of the other abovedescribed concepts. Although an embodiment of this invention has beendisclosed, a worker of ordinary skill in this art would recognize thatcertain modifications would come within the scope of this invention. Forthat reason, the following claims should be studied to determine thetrue scope and content of this invention.

The invention claimed is:
 1. A method for detecting a closing time of an injector valve of a vehicle engine, the method comprising: receiving, at a first control logic, a valve current profile of the injector valve; processing, at a second control logic, the valve current profile using at least a slope discriminator; determining, at the second control logic, an output of the slope discriminator based on the valve current profile; and determining, at a third control logic, based on the output of the slope discriminator: a stuck status of the injector valve, and a closing time of the injector valve when the injector valve is not stuck, by: comparing the output of the slope discriminator to a predetermined closing time detection threshold; determining whether a maximum output value of the slope discriminator is below the predetermined closing detection time detection threshold; if the maximum output value is below the predetermined closing time detection threshold, determining, by the third control logic, that the stuck status is stuck; and if the maximum output value is above the predetermined closing time detection threshold: determining that the stuck status is not stuck, and determining the closing time of the injector valve based on a location of the maximum output value.
 2. The method of claim 1, further comprising starting, at a fourth control logic, a delay timer at an end of an injector current clamp, the method further comprising delaying for a predetermined period of time starting at the end of the injector current clamp prior to the step of receiving the valve current profile of the injector valve, wherein receiving the valve current profile includes collecting valve current data.
 3. The method of claim 1, wherein the step of processing the valve current profile comprises determining median values within a median window and mean values within a mean window.
 4. The method of claim 3, wherein the step of processing the valve current profile comprises calculating a series of mean output data points and a series of median output data points, wherein each median output data point in the median window is a median value of data points within the median window at a corresponding time; wherein the data points within the median window are sorted in increasing value; wherein each mean output data point in the mean window is a mean value of data points within the mean window at a corresponding time; wherein the mean window encompasses fewer data points than the median window; and wherein the mean window begins at a predefined offset from the median window start point.
 5. The method of claim 4, wherein the step of processing the valve current profile comprises generating a slope discriminator output according the relationship Output=median term times gain factor for median term minus (mean term times gain factor for mean term minus offset term), where Output is the slope discriminator output at a given time, median term is the median value of the sorted data points in the median window at the given time, mean term is the mean value of the data points in the mean window at the given time, and the gain factors are variable amplification factors, wherein the gain factor for the median term is one plus the absolute value of the difference between the median value of the sorted data points in the median window at the given time and the mean value of the data points in the mean window at the given time; and the gain factor for the mean term is one minus the absolute value of the difference between the median value of the sorted data points in the median window at the given time and the mean value of the data points in the mean window at the given time.
 6. A method for controlling an injector, the method comprising: instructing, using a controller, an injector to begin closing; receiving, at the controller, an injector current profile of the injector; processing, by the controller, the injector current profile using at least a slope discriminator; determining, by the controller, based on an output of the slope discriminator: a stuck status of the injector; and a closing time of the injector when the injector is not stuck, by: comparing the output of the slope discriminator to a predetermined closing time detection threshold; determining whether a maximum output value of the slope discriminator is below the predetermined closing detection time detection threshold; if the maximum output value is below the predetermined closing time detection threshold, determining that the stuck status is stuck; and if the maximum output value is above the predetermined closing time detection threshold: determining that the stuck status is not stuck, and determining the closing time of the injector based on a location of the maximum output value.
 7. The method of claim 6, further comprising providing the injector as a selective catalytic reduction injector. 